Laser imaging systems have been used for some years to assemble the components of an assembly, such as the components of a truss or the components of an aircraft assembly. The laser imaging system generally includes a computer or controller, a laser scanner projector and a data set defining the pattern of the components of the assembly in the desired orientation and pattern. The laser scanner includes a laser which is projected on mirrors rotatably mounted in parallel perpendicular relation. The rapidly scanning laser image is a laser spot which moves from location to location with sufficient speed to appear to the assembly person as a continuous line. A plurality of images may be projected essentially simultaneously for assembly of a plurality of components, such as the planks and/or the truss connector plates on a flat work surface or the components of an aircraft on a three-dimensional work surface. Such laser assembly systems are available from Virtek Vision Corp., the assignee of the present invention.
It is also common to assemble components using jigs mounted on a work surface, particularly repeated assembly of components in a predetermined pattern or orientation. In assembly of a truss, for example, it is common to mount jigs on a table which in combination define the location and orientation of the components of a particular truss generally for repeated assembly of a truss design. As will be understood by those skilled in the art, trusses are used for roof and floor supports of domestic and commercial buildings. The truss comprises a plurality of elongated planks generally made of wood, steel or other materials arranged in a triangulated pattern which are interconnected by truss connector plates having transverse sharp tangs which are driven into the adjacent planks at the points of intersection or other connection methods. The planks are pre-cut to a predetermined length and angle, and the planks are arranged on the work surface in a predetermined orientation and triangulated pattern for interconnection by the truss connector plates or other fasteners for each truss design. Set-up jigs have been used for many years to facilitate the assembly of trusses having a common design.
Truss assembly tables having pre-mounted moveable jigs or "pucks" are also commercially available. In such truss assembly tables, the work surface includes a plurality of spaced parallel guides and the jigs are slidably mounted on the guides for parallel movement on the work surface. Truss assembly jig tables are also available wherein the jigs are magnetically held to the work table or wherein the jigs include an elongated slot which receives a fastener on the table, permitting orientation of the jigs on the table. Following orientation of the jigs on the work surface, the jigs are fixed relative to the work surface for assembly of a particular truss design. In one preferred embodiment of a truss assembly table, the work surface includes a plurality of spaced parallel channels and the jigs each include a portion which is received in the channel for parallel movement on the work surface.
The assembly of a truss on a jig set-up table of this type then includes moving a plurality of jigs generally in parallel relation on the guides to a predetermined position on the work surface and fixing the jigs relative to the work surface for assembly of a truss design. In the alternative designs of truss jig assembly tables discussed above, the jigs are moved in any direction to the predetermined location and fixed relative to the table. This method, however, remains a time consuming procedure because the location of each of the jigs must be very accurately measured relative to a reference point or line, such as the end of the work table. Further, it is easy to miscalculate the precise predetermined location of one or more jigs, particularly for a large complex truss. Where the error is not immediately determined, the truss may be improperly assembled even where the error is only a fraction of an inch because the errors may be cumulative. Further, the location and orientation of the components of a large complex truss, for example, may not be apparent from the location of the jigs, requiring skilled labor. Thus, such jig set-up tables are generally only used where a substantial number of trusses of the same design are assembled. It would be desirable, however, to use such jig set-up tables even where a limited number of trusses of the same design are assembled. Further, it would be very desirable to reduce the set-up time and improve the accuracy of a jig assembly table of this type and simplify the assembly. Thus, the primary objects of the present invention are to accomplish these purposes by combining the advantages of a laser layout assembly system and jig assembly table.